There are many types of systems that process or use a pressurized fluid, To ensure the safety of these types of systems, each such system typically includes a safety device designed to prevent the over-pressurization of the system. In an emergency situation, where the fluid in the system reaches an unsafe level, the high pressure of the fluid acts on the safety device to create an opening to release fluid from the system. Venting fluid to the environment or a safety reservoir through the opening reduces the pressure in the system and prevents another portion of the system from failing due to the high pressure of the fluid. Examples of known safety devices are disclosed, for example, in U.S. Pat. Nos. 3,472,284, 3,039,482, 2,304,491, 3,603,333, 4,724,857, 4,787,409, 4,930,536, 4,977,918, 5,012,834, 5,067,511, 5,116,089, 5,146,942, 5,209,253, 5,226,442, 5,273,065, 5,297,575, 5,311,898, 5,318,060, 5,348,039, 5,373,864, and 5,433,239.
One type of safety device for a pressurized system is a pressure relief valve, which may be a reclosing valve or a non-reclosing valve. Typically, a spring, a pin, or a combination of a spring and pin, is used to hold a moving plug in sealing engagement with the body or housing of the device while connected to the pressurized system. When the pressure of the fluid reaches the predetermined safety level in such systems, the force exerted on the plug by the pressurized fluid overcomes the bias of the spring or exceeds the resistance of the pin that holds the plug in place. When either of these events occurs, the pressurized fluid moves the plug to expose an opening through which fluid may escape to relieve the pressure in the system. Reclosing valves will automatically reset once the pressurized fluid at the inlet of the device has reduced sufficiently for the spring or other mechanism to reseat the plug. Non-reclosing valves require that the device be manually reset so that the valve plug is re-engaged with the seal and, if necessary, the pin or other expendable component replaced.
One type of pressure relief valve is a rotatable valve assembly. Known rotatable valve assemblies are disclosed in commonly owned U.S. Pat. Nos. 5,607,140, 5,947,445, 6,098,495, 6,367,498, 6,488,044, and 6,491,055, the entire contents of each of which are expressly incorporated herein by reference. A rotatable valve includes a plug that is mounted on a rotatable shaft and may be rotated between a closed position where the plug blocks the flow of fluid and an open position where the plug allows fluid to flow through the valve. The rotation of the plug to the open position may be initiated manually or by another external force. Alternatively, the plug may be mounted on the shaft so that the rotational axis of the plug is offset relative to the center of the plug, so that the pressurized fluid exerts a torque on the shaft and urges the plug to rotate. A device may be coupled to the shaft to prevent the shaft from rotating until the torque on the shaft reaches a certain level, indicating that the pressure of the fluid has reached an over-pressure situation. At that point, the shaft is released and the plug rotates to open the valve and vent the system.
A valve disposed in a pressurized system will often include a seal between the body and the plug to limit or prevent fluid from leaking through the valve. As illustrated, for example, in U.S. Pat. No. 6,367,498, a known seal is disposed in a valve body and is configured to engage with the outer perimeter of the valve plug to prevent pressurized fluid from flowing between the plug and the body while the valve is closed. Because a known seal is disposed in a valve body, it is held stationary while the valve plug rotates. As such, there is limited control over the sealing mechanism, including the interface between moving and non-moving parts of the valve assembly. In addition, the valve body is subject to deformation in the event of irregular loading within the piping or another portion of a pressurized system. Such irregular loading can deform a seal provided within the valve body, thereby negatively affecting the seal's performance. To replace a known seal provided in the valve body, the valve must be disassembled, which may be costly and time-consuming. Additionally, a known valve positions the seal perpendicular to the flow when the valve is open, which may increase the risk that the seal could be damaged and/or torn out as fluid passes through the valve.
There is a need for a pressure relief device that overcomes one or more of the deficiencies above and/or other deficiencies in the art, and/or provides additional benefits.